(1) Field of the Invention
The present invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of simultaneously recrystallizing the source/drain regions and removing native oxide in the fabrication of integrated circuits.
(2) Description of the Prior Art
In the fabrication of integrated circuit devices, logic products are often produced using salicide (self-aligned silicide) processes in order to obtain higher circuit performance. In silicidation, a refractory metal layer is deposited and then annealed. The underlying silicon reacts with the refractory metal layer to produce a silicide overlying the gate electrode and source and drain regions. The silicided gate and source/drain regions have lower resistance than non-silicided regions, especially in smaller geometries, and hence, higher circuit performance.
Before metal deposition for silicidation of the source/drain regions, native oxide formed over the source/drain regions must be removed so that lower contact resistance can be obtained. This is usually done using a hydrofluoric acid (HF) dip or by sputter etching. A disadvantage of sputter etching is that plasma damage to the underlying source/drain region may occur. An HF dip does not damage the source/drain region, but is environmentally hazardous.
After source/drain implantation, an annealing process, typically a rapid thermal process (RTP) in nitrogen, must be performed to repair the crystal structure of the silicon in the source/drain regions. It would be desirable to combine the recrystallization and removal of native oxide to be performed simultaneously.
U.S. Pat. No. 5,863,820 to Huang teaches a salicide process. U.S. Pat. No. 5,646,057 to Liu et al teaches a RTP annealing at high temperature followed by annealing at low temperature using H2to improve performance. No mention is made of removing native oxide. U.S. Pat. No. 5,418,184 to Girisch teaches adding a hydrogen halide to a nitrogen anneal and a subsequent step to remove native oxide. U.S. Pat. No. 5,219,798 to Kamakura describes a method to prevent recrystallization defects by spraying Hz on the underside of a substrate in order to cool it during annealing. U.S. Pat. No. 4,522,657 to Rohatgi et al shows a hydrogen ion implantation followed by a low temperature annealing in nitrogen.